Basic loss per share is calculated by dividing net loss attributable to common stockholders by the weighted-average number of common shares. Diluted loss per share reflects additional common shares that would have been outstanding if dilutive potential common shares had been issued. Potential common shares that may be issued by the Company include convertible preferred stock, options and warrants.

Diluted loss per common share for the nine-month periods ended September 30, 2021 and 2020 excludes the effects of 1,685,104 and 1,521,844 common share equivalents, respectively, since such inclusion would be anti-dilutive. The excluded shares consist of common shares issuable upon exercise of outstanding stock options and warrants.

The Company’s unvested restricted stock awards contain nonforfeitable rights to dividends or dividend equivalents, whether paid or unpaid (referred to as “participating securities”). Therefore, the unvested restricted stock awards are required to be included in the number of shares outstanding for both basic and diluted earnings per share calculations. However, due to our loss from continuing operations, 38,333 and 60,000 shares of unvested restricted stock for the nine-month periods ended September 30, 2021 and 2020, respectively, were excluded in determining basic and diluted loss per share from operations because such inclusion would be anti-dilutive.